In an industrial plant, movable wireless sensors may be used. It may be desirable to be able to locate these sensors within the plant. For this, stationary beacons of known position can be used. The location of the sensor may then be calculated e.g. via triangulation or by estimating the distance between each of the beacons and the sensor by measuring the attenuation of each of the beacon signals when it reaches the sensor. The weaker the signal, the further away is the beacon.
Wireless sensor networks are disclosed in the patent publications WO 2011/040346, U.S. Pat. No. 7,812,718 and US 2010/085242.
US 2011/0105142 discloses, as a prior art therein, a method where a wireless communication device estimates the location of itself based on triangulation by using reception strength of a beacon regularly transmitted from a base station and location information of the base station included in the beacon. According to this method, the wireless communication device has to receive beacons from at least three base stations.